Nuclear association of nonmuscle myosin-ii within the giant cells of drosophila melanogaster salivary gland organ: Tail domain specifies perinuclear oligomerization

It is know from in vitro experiments that contractile forces of nonmuscle myosin-II (MyoII) in the cytoplasm affect the function of the nucleus. Furthermore, perinuclear pools of MyoII have been localized among several types of cultured cells. However, beyond cell culture experiments there is no evidence that cytoplasmic MyoII associates with the nucleus. The aim of the current experiments is to determine whether or not MyoII associates with the nucleus of cells in metazoan tissue. The giant cells within salivary gland organs from 3rd instar Drosophila melanogaster larvae were evaluated in living and fixed preparations. A UAS-Gal4 conditional expression system was used to drive gene expression of MyoII specifically within salivary gland organs. A GFP-MyoII protein trap line which uses the endogenous MyoII promoter to control expression of full-length GFP-MyoII was also employed. Additionally, antibody immun ore activity was used to localize endogenous MyoII proteins. The results revealed a perinuclear localization pattern for the Myoll molecule. The molecule formed oligomerized (filament-like) conformations on the cytoplasmic side of the nuclear lamin. Furthermore, the Myoll α-helical coiled-coil tail was shown to be necessary for perinuclear localization and oligomerization. These experiments provide direct evidence for a nuclear association of MyoII within metazoan tissue.